In a liquid crystal display device, a TFT substrate in which pixel electrodes, thin film transistors (TFTs), and the like are formed in matrix is disposed facing a color filter substrate in which color filters and the like are formed at positions corresponding to the pixel electrodes of the TFT substrate. Liquid crystal is provided between the TFT substrate and the color filter substrate. The liquid crystal display device controls the transmittance of light of the liquid crystal molecules for each pixel to form an image.
The liquid crystal display device can be reduced in size and thickness, and is used in a wide range of applications such as cellular phones. Recent cellular phones have a variety of applications. Further, input devices are also expected to have a function allowing finger input through a touch panel, in addition to the conventional key-button operation. In such a case, the touch panel is mounted on the side of the color filter substrate of the liquid crystal display panel.
Meanwhile, in the liquid crystal display device, there is a strong demand for reducing the thickness of the liquid crystal display panel, in addition to reducing the overall size of the set while keeping a certain size of the screen. The thickness of the liquid crystal display panel is reduced by polishing the outside of the liquid crystal display panel after production of the liquid crystal display panel. A liquid crystal display panel includes a TFT substrate in which pixel electrodes, thin film transistors (TFTs), and the like are formed, as well as a color filter substrate in which color filters are formed. The TFT substrate and the color filter substrate are glass substrates that are standardized, for example, to 0.5 mm or 0.7 mm. It is difficult to obtain such standardized glass substrates from the market. In addition, very thin glass substrates have a problem relating to mechanical strength and bending in the production process, leading to a reduction in the production yield. As a result, the liquid crystal display panel is formed with the standardized glass substrates, and then the outside of the liquid crystal display panel is polished to reduce the thickness of the liquid crystal display panel.
The reduction of the thickness of the liquid crystal display panel poses a problem of the mechanical strength. When a mechanical stress is applied to the display surface of the liquid crystal display panel, there is a risk that the liquid crystal display panel will be broken. The situation is the same with the liquid crystal display panel in which a touch panel is set when the touch panel is made of glass.
In order to prevent the liquid crystal display panel from being broken by outside force, a front window of resin or glass is attached to the screen side of the liquid crystal display panel. In this case, an air layer exists between the liquid crystal display panel and the touch panel, or between the touch panel and the front window. The transmittance of the light from the backlight is reduced by the reflection from the interface in this area.
In order to prevent this, JP-A No. 83491/2008 describes a configuration in which an adhesive layer or an anti-reflection coating is formed between the liquid crystal display panel and the touch panel or between the touch panel and the front window.